The present invention relates to a carbon dioxide gas absorbent, a method for manufacturing carbon dioxide gas absorbent and an apparatus for separating carbon dioxide gas, which are used for the separation and collection of carbon dioxide gas from a fuel gas or an exhaust gas in an energy plant which uses a fuel whose main component is hydrocarbon.
Known examples of the method of separating carbon dioxide gas from an exhaust gas are a type which utilizes a cellulose acetate film and a type which utilizes the chemical absorption process by an alkanol amine-based solvent.
However, in any of these example methods, it is required to set the upper limit of the temperature of the introduction gas to about 200.degree. C. in consideration of the heat resisting properties of the materials for the film, solvent and the like employed in these methods. Therefore, in the case where carbon dioxide gas is separated from a system which exhaust a high-temperature exhaust gas, it is required to cool down the exhaust gas by a heat exchanger or the like, despite that the heat of the exhaust gas could be utilized in some way. Thus, as a result, the energy consumed for the separation of carbon dioxide gas increases, and therefore the usage of these methods is very much limited.
Under these circumstances, the inventors of the present invention have proposed the method of separating a carbon dioxide gas, which uses lithium zirconia (Jpn. Pat. Appln. KOKAI Publication No. 9-99214). With this method, it is possible to separate a carbon dioxide gas without undergoing a cooling step for cooling the high-temperature exhaust gas.
The above-mentioned KOKAI publication discloses the use of a carbon dioxide gas absorbent in the following manner. That is, lithium zirconia powder is mixed with a solvent and a binder to prepare a slurry, and the slurry is processed by a doctor blade method into a film having a porosity of about 55%. Then, after degreasing, a carbonate salt mixture of lithium carbonate and potassium carbonate are molten and impregnated into the porous film, thus obtaining a carbon dioxide gas absorbent.
However, the carbon dioxide gas absorbent disclosed in the publication does not exhibit a sufficient performance in the absorbing property of carbon dioxide gas at an initial stage of use.